PURPOSE: To reduce the loss of air-flow rate of an air conditioner, by disposing a vertically deflecting vane plate utilizing the Coanda effect adjacently of a fixed guide plate in the manner that it can be turned pivotally, so that the direction of discharge air can be changed smoothly over a large angle in the vertical direction.

CONSTITUTION: During space-heating operation, a vertically deflecting vane plate 14 is turned vertically, while the horizontal direction of warm air supplied from a lateral-flow fan 4 is determined by horizontally deflecting vanes 12, so that the warm air is discharged substantially in a downward direction by the function of a fixed guide plate 10 and the vertical deflector plate 14 disposed adjacently of the fixed guide plate 10. Here, both of the fixed guide plate 10 and the vertical deflector plate 14 are designed to have an aerofoil section, so that warm air can be discharged without resistance and smoothly by the aid of the Coanda effect. In space-cooling operation, on the other hand, the vertical deflector plate 14 is turned to a substantially horizontal position, so that cool air is discharged substantially in a horizontal direction, guided by the fixed guide plate 10 and the vane plate 14 by the Coanda effect.